Displays which are based on electro-optical effects such as LCDs, OLEDs, and electrophoretic displays are often addressed using an array of ‘active’ devices. These provide a non-linear disconnection between the matrixing of the information and the electric field or current at each pixel. Typically a thin film transistor (TFT) is used such that its gate is controlled in parallel with all other devices on a particular row, and its source is provided by a data driver connected to each column. The drain is connected to the pixel driving electrode and optionally a capacitor to provide an effective ‘sample and hold’ of the data voltage. When arranged as a large row and column matrix a full image display can be effected. In a matrix there is the additional complication that the source lines must cross the gate lines (or vice versa) either at the device, or independently.
International patent applications WO2005/008744 and WO2005/009095 describe a technique which is based on the electroforming of all of the metal contacts and connections to a TFT device and the formation by ‘overgrown’ electrodeposition of crossover features. The second layer dielectric, which forms either the gate layer dielectric or the crossover dielectric, is formed by photo- or laser-patterning of a suitable polymer material.